1. Field of the Invention
The present invention relates to the provision of a system for providing forward thrust for a boring tool. More particularly, the invention provides the necessary thrust for the operation of a rotary boring tool in situations, such as the drilling of generally horizontal bore holes, where the force of gravity does not act to provide effective forward thrust. The invention is especially efficacious with flexible drill pipe or conduit such as may be used in drilling highly deviated bore holes.
2. Description of the Prior Art
Hydraulic power has been used to rotate boring tool in drilling vertical and deviated bore holes for many years. Typical of such tools is the Dyna-Drill, offered by the Dyna-Drill Company, a division of Smith International, Inc. of Irvine, California. The power generated by the Dyna-Drill is used and only used to rotate the drilling bit. The system is used with conventional drill pipe and drill collars to provide the desired weight on bit or thrust.
A. McDougall, U.S. Pat. No. 469,841 discloses a system for dredging in which a boring tool is mounted on the same shaft as a propeller. Flow of liquid circulated for the dredging operation causes both to rotate. Thrust for the boring tool, however, is obtained by the weight of the system. The reverse circulation system disclosed actually tends to lift McDougall's boring tool rather than to advance it.
A water jet propelled nozzle head for cleaning pipes and conduits is disclosed by U.S. Pat. No. 2,710,980 to Pletcher in which jets direct water against vanes to rotate an outer section relative to an inner section which is fixedly secured to a hose. Neither the rotative nor the advancing force developed is adequate for subsurface earth boring.
Kirschke, U.S. Pat. No. 3,432,872, shows a jet propelled hydraulic pipeline cleaner having a vaned rotor and radial and tangential jets. The device is cumbersome and is not suited to earth boring.
Masters, U.S. Pat. No. 3,525,112, proposes a rotary root cutting head for use in sewer pipe having rearwardly facing nozzles to impell the head forwardly and tangential nozzles in a rotor. The system is not serviceable in underground boring due to lack of sufficient advancing and rotative force and because of its structural configuration.
Elbert, U.S. Pat. No. 3,844,362, discloses a boring device which utilizes ejected fluid to provide rotative torque and to assist in driving the device forward. The advancing force developed is clearly insufficient to cut into an earth formation and also tug a hose into a lateral passageway of useful length.
More generally, the prior art is rich in the field of drilling directionally deviated wells using rotary bits turned from the surface or by subsurface mud turbines. However, such boring means are not self-advancing in generally horizontal bore holes, do not have non-stalling characteristics and are unable to form sharply curved bores, all of which constitute advantages of the instant invention.